The major goal of this research training program is to train the future leaders of medical genetics who will emerge from a variety of training pathways with varying amounts of research experience. Many will have M.D. degrees, others will be M.D.-Ph.D.'s with clinical training in Pediatrics, Medicine, Psychiatry, Pathology and other specialty areas will be eligible for support from this training grant. Combined pediatric-genetics residents will also be eligible during their 4th and 5th years of residency. Funding for 5 training slots per year is sought. The overall training program for these individuals consists of one clinical year during which the resident/fellow has a substantial clinical load and fulfills a portion of her/his didactic course work in human genetics and molecular biology. This first year is funded by the University of Pennsylvania School of Medicine and The Children's Hospital of Philadelphia (CHOP), while funds for the research years of the overall training program are sought from this training grant. During the second year, the M.D. resident/fellow completes didactic course work and begins research training. During most of the second year and all of the third year and often the fourth years, the fellow devotes essentially 100% effort to research in a basic science laboratory. Research opportunities are extremely diverse with training in the laboratories of 43 Faculty from 6 core departments at Penn. Fields of research may encompass those areas that impact human genetics including, but not limited to: molecular genetics, cytogenomics, biochemical genetics, mitochondrial genetics, developmental biology, cellular biology, bioinformatics, systems biology, pharmacogenetics and others. During the research years, the trainee also takes seminar courses, attends journal clubs, research meetings, and departmental research retreats, and carries out minimal clinical activities, not to exceed 5% effort. Training stipends for the 2-3 years of research are requested in this application. The M.D. trainee will likely require further research training (not covered by this training grant), which might be acquired through an additional postdoctoral research experience or a protected faculty appointment with considerable mentoring from a senior faculty member.